Rust bluing a modern o/u barrel from some Italian maker. Proper preparations were done. The middle rib is not taking finish as well as the tubes. I’m using Laurel Mtn.. Not sure how to address this, other than perhaps some targeted treatments just to the rib with some Mark Lee. Would appreciate your suggestions. Thanks!

If you can heat the rib a bit, apply some LM Express Blue before you boil to the section that's not taking. It only needs to be hot enough to evaporate the solution quickly.

Rust blue reacts differently with different metals.
Usually a few additional coats will make it even out.
Chuck

Not always a guarantee but worth a try, I make up a rapid rust solution for spot fixing though colour may be a problem. It is a simple mixture of Salt, White Vinegar, Hydrogen peroxide. Let it rust, card, then pour boiling water from a kettle over the area. It is one of those processes in the realms of "Suck it and see". Keep an eye on things if the atmosphere is at all damp rust will form before your eyes so do not leave it on too long things are very dependent on the strength of the Hydrogen Peroxide you use.

What’s happening, even with Mark Lee use, is that the rib looks great, and then you wipe oil on it, or gently rub with baking soda to neutralize the rusting agent, and the bluing wipes off the mid rib. Owner says gun has never looked good, and that the maker was originally an aerospace company. Not sure what the rib it made of, but it’s weird. Maybe it was hot blued originally.

This is the side rib(s) you are having the problems with on an O/U,,,not a top rib? ('Middle rib'?)

Who knows what they can be made from these days of miracle fabrication processes.


Have you polished them at all to roughen up the surface of the rib? or are you bluing just over the cleaned orig polish metal?
If the latter, I'd pick a small area out of sight (under the forend?) and polish it a bit with something like 220 or 280grit,,fairly rough. Something for the soln to bite into.

What you describe is what used to be a common problem in rust bluing small parts that had been case hardened,,like early Springfield 03 bolt parts.
They'd rust, they'd turn blue, but with just a bit of handling or some oil on them the blue would come right off and leave you with grey colored steel parts.
The cure was to etch them with weak acid for the same reason as above.

Hope it helps.

Side rib, the rib between the barrels. Top rib is fine. I had polished them to 220. What kind of acid would be used to etch them first. I have ferric chloride around, and muratic as well.

If nothing helps, I may be that I just advise the fellow to mask off the rib and Cerakote the rib, or the whole barrel.

We used to use diluted muriatic acid (about 10% acid IIRC) to etch small parts,,but we did it with parts being warm as just pulled out of the hot water tank.
They etched instantly then a quick dunking back in the water and back out and a coating of Express Rust blue on them and off you went.
This etching was just done once, before the first coating of bluing soln was applied.

If you wanted to try an etch, I'd go with the ferric chloride as in a damascus finish etch.
A quick in and out cold dunking with the bores protected. Let the entire assembly etch,,tubes, ribs, ect and rinse off. Then procede to bluing.
Certainly worth a try at this point.

That's about a last resort.

If you don't want to try it, then the Cerakote idea comes into play I guess.
Those ribs may even be a rust resistant alloy as you can get them to rust a bit, but it comes right back off.

Modern guns,,what a pain!

Bill, if you are using a damp box try upping the humidity . Proceed with caution as things can happed in a hurry. Put the barrel in and let it get up to temp then add humidity this reduces the risk of sweating

The maker of the gun is Marocchi. Does anyone know what their o/u barrel factory finish is?

I’m thinking Ceracote is the way to go. Had good success recently with an older chrome SKB SxS barrel, which clearly wouldn’t blue.

B. Graham,
My daughter and son in law work in the Research Triangle, the next time they come home, I can send you a little German solution to try. It won't help for this problem, but maybe another one.
Mike

Thanks Mike, that’s very kind of you. I’d be pleased to try your solution.

It will be several months before they come home again, so PM me with your address and telephone number, whenever you get a chance.
Mike

Update: hot bluing took care of it. Confirmed beforehand that this was the factory finish. All is well. Happy owner/friend.